The subway train ground to a halt in the city of Fukuoka after the man used the button to tell the local transportation bureau: “There’s a person coughing and they’re not wearing a mask”, The Mainichi newspaper reported.
The service stopped at Befu station, where it was delayed for several minutes while the stationmaster tried to calm the two quarrelling men down.
The pair, who had been sitting next to each other, reportedly reconciled after stepping out onto the platform.
A city transport official told Kyodo news agency that “fear” of the coronavirus, which has affected tens of thousands of people across the globe, “is spreading among passengers”.
A spokesperson for the transportation bureau told The Mainichi: “We’d like to ask people to refrain from pushing the emergency notification button just because there is someone without a mask.
“We’re calling on passengers to show proper manners when they cough, and want to publicise this more.”
The new coronavirus, officially named Covid, has infected more than 76,000 people in 27 countries and caused more than 2,200 deaths since it was first reported in China’s Hubei province in December.
The Diamond Princess cruise ship, quarantined at a port in Yokohama, has the most cases of the new virus outside of China, with over 600 cases confirmed by late Thursday.
Two passengers died after contracting the virus on board the cruise ship.
The Japanese couple, in their 80s, died in hospital after being taken off the vessel last week.
Their deaths raised Japan’s death toll from one to three.